HSQLDB has the user guide on their website for the latest version of it. This differs greatly from the version that LO uses.
LO uses v 1.8 which is hard to find on the Internet, so I have uploaded my copy of the PDF version to the Base folder, Draft folder of Alfresco. It should probably be included in the published Base documentation. This way people who need it will be have a place to get it, and I will have a URL to list in the Base Guide for this purpose.
--Dan